Towards a better assessment of hydrological natural variability as a key adaptation strategy to climate change

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Despite all the research done on the impacts of climate change on water resources, few stakeholders have been willing to commit to adaptation strategies for a distant and uncertain future. Decision makers are more prepared to adapt to strategies with a shorter return on investment (<20 years). Over a 20-year horizon however, climate is strongly dominated by natural variability and not by human-induced change. In many cases, infrastructures are not well adapted to natural climate variability (let alone climate change), because it is essentially overlooked in engineering design which usually assumes stationary stochastic processes.****Consequently, adaptation to natural variability would be an efficient way to reduce vulnerabilities in the current and future climate. With an adequate knowledge of natural variability, robust no-regrets adaptation strategies could be devised. These strategies would be easier to sell to stakeholders because they would not be as clouded with uncertainties as those derived from climate change impact studies. This research program proposes an in-depth look at natural climate variability in hydrological sciences and how to harvest this knowledge to eventually improve engineering design practices and provide robust adaptation strategies to climate change. The main objectives are to:****o Better describe and understand the natural variability of key hydrological variables over Canadian watersheds; and***o Contrast the relative contributions of natural variability and climate change to hydrological vulnerability in both current and future climates.******To move toward these long term goals, the following four specific objectives are proposed:****- Study the natural climate variability on selected watersheds using the longest available traditional time-series;***- Extend the historical record for key stations and watersheds using output data from the 20th century reanalysis project and long-range meteorological gridded data, combined with hydrological modelling;***- Further our understanding of natural variability using three large ensembles of climate model simulations; and***- Based on the 1980-2010 reference period, to contrast the impacts of natural variability and climate change for various future time horizons.******This research program will provide stakeholders with a better understanding of our vulnerabilities to natural climate variability. Adapting to natural variability, as opposed to climate change, is likely to translate into more rapid actions by decision makers, while affording a significant protection against climate change. Considering that the cost of climate change in Canada is evaluated at between 21 and 43 billion dollars per year by 2050, any successful adaptation strategy will result in a very large saving for the Canadian economy.**